Elongated, flexible guide units are often used in medical procedures to gain access to specific inner areas of the body without major surgery. Guide units may be passed into the body via peripheral blood vessels, the gastrointestinal tract, or the urinary tract. Guide units, often referred to as guide wires, are commercially available and are currently used in cardiology, gastroenterology, urology, and radiology. Once in place, guide wires serve as guides for the safe introduction of additional medical instruments such as catheters.
To facilitate threading a guide through a predetermined body channel such as an artery, the guide may include a generally flexible body portion which is resistant to kinking and a forward end portion of increased flexibility, the end portion terminating in a smoothly rounded tip. The body portion may include a core of stainless steel or other metal, the core being appropriately dimensioned in cross section to provide the desired degree of flexibility to the guide wire. A coating of plastic or the like may be applied over the surface of the core, if desired. To provide greater flexibility to the guide at its forward end, the forward end of the core may include a section of lesser diameter and hence of greater flexibility. Optionally, the core may terminate at a position spaced from the guide end, thus providing the guide end with increased flexibility. A flexible length of helically wound wire forming an elongated coil ma be employed at the forward end of the guide wire and may extend throughout the length of the guide unit. A small button or plug commonly is employed at the forward end of the coil to provide the guide with a smoothly rounded tip.
When a guide is to be removed from a body channel such as an artery, the forward, end of the guide can unintentionally become detached from the body of the guide wire and hence may remain behind in the artery when the guide wire is withdrawn. In an attempt to prevent this from occurring, researchers have employed safety wires which may extend substantially throughout the length of a catheter and which are soldered or otherwise adhered to the forward button so that the button and coil can be retrieved together with the remainder of the guide wire when the latter is withdrawn from an artery. The safety wire may be of a flattened wire and may lie along side the core Alternatively, the metal core may have a tapered, forward end portion that functions as a safety wire and that is attached to the forward button. Reference is made particularly to U.S. Pat. No. 4,003,369 and 3,612,058 as showing guide wire embodiments of the type described.
Unfortunately, the attachment via solder or other adhesive of safety wires to the forward buttons in guide wires of the type described generally is not particularly strong. It appears that failure occurs generally in the soldered or other adhesive bond between the forward end of the safety wire an the metal button at the forward end of the guide wire. It would be desirable to provide a flexible guide having a forward tip which is far more securely fastened to the body of the guide.